1. Field of the Invention
This invention relates generally to systems for testing electrical and mechanical energy transfer systems that exhibit vibratory and other responses to electrical or mechanical input energy, and more particularly, to an arrangement that isolates a mechanical or electrical system under test and produces signals and data corresponding to a plurality of operating characteristics of the system under test in response to the input energy.
2. Description of the Related Art
Noise testing of gears to date has been attempted by methods that rigidly mount the gear or axle assemblies in one or more planes. Some other previous attempts chose to have one of the rigidly mounted planes resonate at a frequency sympathetic to gear noise. None of these methods, or any other rigidly mounted test system has been successful. This is due to the lack of repeatability of the previous systems, largely as a result of interacting resonances, and external background noise that is transferred through the rigid mounting system. This is especially true in a production test environment.
These deficiencies in the prior art are most evident in the axle industry. At this time, the only widely accepted way of measuring gear noise is to acquire an assembled axle and install it in a test car. A specially trained individual then drives the car over its typical operating range while carefully listening for axle gear noise. The individual rates the quality of axle gear noise on a scale that is typically 0 to 10. Ten is usually a perfect axle, i.e. one that has no gear noise. This method is made difficult by:
1 The lack of available trained noise rating individuals
2 The cost of test cars.
3 The lack of quality roads or test tracks on which to perform a repeatable and accurate test.
4 The time required for each test.
5 The subjectivity that humans bring into the rating system
Typically less than a dozen axles can be tested by a major manufacturer in one shift due to all of the above complications. This low number is not statistically valid when it is considered that most manufacturers make thousands of axles each day. Even with all of the above problems, human testers in cars are the only widely accepted method of axle testing in the industry due to the lack of a better more reliable testing method. This lack of a scientific basis for rating axles and gear systems is made worse when the reader considers that modern cars are extremely quiet, and are evolving to become more quite. This market direction increases the pressure on axle and other gear manufacturers to make their products quieter. There is a need for a system that offers gear and axle manufacturers a repeatable, reliable, accurate and practical way of measuring gear noise in production or laboratory environments.
It is, therefore, an object of this invention to provide a system for testing an energy transfer system, such as a vehicle axle, quickly and inexpensively, and achieving repeatable results.
The foregoing and other objects are achieved by this invention which provides, in a first apparatus aspect thereof, a drive coupling arrangement for transmitting substantially exclusively torque from a drive arrangement to a gear assembly under test. In accordance with the invention, the drive coupling arrangement is provided with a first coupler portion attached to the gear assembly under test. The coupler has a polygonal cross-sectional configuration that extends continuously over a predetermined length of axis. The polygonal cross-sectional configuration has a plurality of substantially planar surfaces that extend parallel to the predetermined length of axis. In addition, there is provided a second coupler portion with an internal cross-sectional configuration that accommodates the polygonal cross-sectional configuration of the first coupler portion. The second coupler portion has a plurality of engagement portions that communicate exclusively with a predetermined number of the substantially planar surfaces of the first coupler portion. The second coupler is axially translatable along the first coupler portion for a portion of its predetermined length of axis. In this manner, the first and second coupler portions exert a torque against one another via the substantially planar surfaces of the first coupler portion and the engagement portions of the second coupler portion, over a predetermined range of the portion of the predetermined length of axis. In addition, a resilient insert is installed within the second coupler portion for limiting the extent of axial translation between the plurality of engagement portions of said second coupler portion along said first coupler portion.
In one embodiment of the invention, the first coupler portion is in the form of an assembly nut of the gear assembly under test at a rotatory terminal thereof. The polygonal cross-sectional configuration corresponds to a hexagon and has six substantially planar surfaces. The second coupler portion has three engagement portions that engage three respective substantially planar surfaces of the first coupler portion. The second coupler portion is coupled to the drive arrangement.
A resilient biasing element urges the second coupler portion axially toward the first coupler portion. The predetermined length of axis is substantially vertically arranged, the first coupler portion being disposed axially superior to the second coupler portion. The resilient biasing element urges the second coupler portion axially upward toward the first coupler portion, whereby the first coupler portion communicates axially with the resilient insert. In a specific illustrative embodiment of the invention, the resilient insert is formed of ultra-high molecular weight polyethylene and absorbs axial loading between the first and second coupler portions.
In accordance with a further apparatus aspect of the invention, there is provided an arrangement for isolating an energy transfer system while it is subjected to a test process for noise, the energy transfer system being of the type having an energy input and at least one energy output. In accordance with the invention, the arrangement is provided with a base for supporting the arrangement and the energy transfer system. An isolation support supports the energy transfer system whereby the energy transfer system is translatable in at least one plane of freedom with respect to the base. Additionally, an engagement arrangement is provided for securing the energy transfer system to the isolation support, the engagement arrangement having a first position with respect to the base wherein the energy transfer system is installable on, and removable from, the isolation support, and a second position wherein the energy transfer system is secured to the isolation support. A first coupler portion is attached to the gear system, the coupler portion having a polygonal cross-sectional configuration that extends continuously over a predetermined length of axis. The polygonal cross-sectional configuration has a plurality of substantially planar surfaces that extend parallel to the predetermined length of axis. There is additionally provided a second coupler portion having an internal cross-sectional configuration that accommodates the polygonal cross-sectional configuration of the first coupler portion. The second coupler portion has a plurality of engagement portions that communicate exclusively with a predetermined number of the substantially planar surfaces of the first coupler portion, and are axially translatable along the first coupler portion for a portion of the predetermined length of axis. Thus, the first and second coupler portions exert a torque against one another via the substantially planar surfaces of the first coupler portion and the engagement portions of the second coupler portion.
In one embodiment, there is further provided an energy supply coupled to the energy transfer system for supplying energy thereto when the engagement arrangement is in the second position. The energy transfer system is, in one embodiment of the arrangement of the present invention, a mechanical energy transfer system, and in such an embodiment, the energy supply, which is a part of the arrangement of the invention, is in the form of a source of rotatory mechanical energy. A rotatory coupler couples the source of rotatory mechanical energy to the energy transfer system. The first coupler portion, in this embodiment of the invention, is an hexagonal assembly nut. The second coupler portion is resiliently urged toward the first coupler portion by operation of a resilient spring.
In a highly advantageous embodiment of the invention, the mechanical energy transfer system test has forward and reverse directions of operation, and drive and coast modes of operation for each of the forward and reverse directions of operation. The mechanical energy transfer system contains at least a pair of meshed elements, at least one of the pair of meshed elements being a gear having a plurality of gear teeth thereon, the gear teeth each having first and second gear tooth surfaces for communicating with the other element of the pair of meshed elements. A mechanical energy transfer communication between the pair of meshed elements is effected primarily via the respective first gear tooth surfaces during forward-drive and reverse-coast modes of operation, and primarily via the respective second gear tooth surfaces during forward-coast and reverse-drive modes of operation. With such a system under test, the arrangement of the present invention is provided with a first acoustic sensor arranged at a first location in the vicinity of the mechanical energy transfer system for producing a first signal that is responsive substantially to a qualitative condition of the first gear tooth surfaces. A second acoustic sensor is arranged at a second location in the vicinity of the mechanical energy transfer system, and produces a second signal that is responsive substantially to a qualitative condition of the second gear tooth surfaces. The first and second locations are distal from each other on opposite sides of the pair of meshed elements.
In a further embodiment of the invention, the rotatory coupler is provided with a resilient coupler arrangement that transmits rotatory motion thereacross over a predetermined range of rotatory motion transmission angles. The resilient coupler arrangement is provided with first and second coupler portions, the first and second coupler portions being rigidly coupled rotationally to each other. Additionally, they are axially resiliently coupled to each other, whereby the first and second coupler portions are synchronously rotatable over the predetermined range of rotatory motion transmission angles.
In yet a further embodiment of the invention, the resilient coupler arrangement is provided with first and second coupler portions, the first and second coupler portions being rigidly coupled rotationally to each other, and radially resiliently coupled to each other. Thus, the first and second coupler portions are synchronously rotatable over a predetermined range of axial displacement.
A torque sensor advantageously is interposed, in a highly advantageous embodiment, between the source of rotatory mechanical energy and the energy transfer system. The torque sensor produces a signal that is responsive to a torque applied by the source of rotatory mechanical energy to the energy transfer system. The torque sensor is provided with a torque-transmitting element that has a predetermined deformation characteristic. Thus, the torque-transmitting element becomes deformed in response to the torque that is applied by the source of rotatory mechanical energy to the energy transfer system. In this embodiment of the invention, the torque sensor further is provided with a strain sensor that is coupled to the torque-transmitting element for producing a strain signal responsive to the predetermined deformation characteristic of the torque-transmitting element. The strain signal, therefore, is proportional to the torque.
It is very advantageous to determine the residual torque required to initiate motion of the system under test. The torque sensor is therefore arranged to produce a static torque signal that is responsive to the magnitude of the torque required to initiate rotatory motion in the mechanical energy transfer system. In addition, it is advantageous that the torque sensor be arranged to produce a dynamic torque signal that is responsive to the magnitude of torque required to maintain rotatory motion in the mechanical energy transfer system.
In accordance with a further apparatus aspect of the invention. there is provided an arrangement for isolating a mechanical drive system for a vehicle while it is subjected to a testing process, the drive system being of the type having a rotatory input and at least one rotatory output. In accordance with the invention, the arrangement is provided with a base for supporting the arrangement and the mechanical drive system. An isolation support supports the mechanical drive system whereby the mechanical drive system is translatable in at least one plane of freedom with respect to the base. An engagement arrangement secures the mechanical drive system to the isolation support, the engagement arrangement having a first position with respect to the base wherein the mechanical drive system is installable on, and removable from, the isolation support, and a second position wherein the mechanical drive system is secured to the isolation support. An engagement driver is coupled to the base and to the engagement arrangement for urging the engagement arrangement between the first and second positions. The engagement arrangement is coupled to the engagement driver when the engagement arrangement is in the first position, and isolated from the engagement driver when the engagement arrangement is in the second position. In addition, a rotatory drive applies a rotatory drive force to the mechanical drive system, and a drive coupler transmits a torque from the rotatory drive to the rotatory input of the mechanical drive system. The drive coupler is itself provided with a first coupler portion attached to the mechanical drive system, the coupler having a polygonal cross-sectional configuration that extends continuously over a predetermined length of axis. The polygonal cross-sectional configuration has a plurality of substantially planar surfaces that extend parallel to the predetermined length of axis. Additionally, the drive coupler is provided with a second coupler portion having an internal cross-sectional configuration that accommodates the polygonal cross-sectional configuration of said first coupler portion. The second coupler portion has a plurality of engagement portions that communicate exclusively with a predetermined number of the substantially planar surfaces of said first coupler portion, and are axially translatable along the first coupler portion for a portion of the predetermined length of axis. Thus, the first and second coupler portions exert a torque against one another via the substantially planar surfaces of said first coupler portion and the engagement portions of the second coupler portion, over a predetermined range of the portion of the predetermined length of axis.
In a mechanical embodiment of the invention. there are additionally provided a rotatory load for applying a rotatory load to the mechanical drive system, and a load coupler for coupling the rotatory load to the rotatory input of the mechanical drive system. The mechanical drive system is in the form of a drive-transmitting component for a motor vehicle. In such an embodiment, the rotatory load applies a controllable rotatory load thereto to simulate a plurality of vehicle operating conditions. These include, for example, gear drive and coast conditions, as well as a gear float condition.
In accordance with a method aspect of the invention, there is provided a method of testing a gear assembly of the type having an input and an output. The method includes the steps of:
installing the gear assembly on a mounting arrangement that resiliently permits motion of
installing the gear assembly on a mounting arrangement that resiliently permits motion of the gear assembly in all directions, the gear assembly having an hexagonal assembly nut installed at a rotatory input thereof;
urging a coupler having three engagement surfaces resiliently and continuously toward the hexagonal nut, whereby the three engagement surfaces communicate with three corresponding surfaces of the hexagonal assembly nut;
applying a torque at the coupler, whereby the gear assembly is rotatably operated;
applying a load at the output of the gear assembly; and
sensing a predetermined operating characteristic of the gear assembly.
In one embodiment of this method aspect of the invention, the step of sensing is provided with the step of detecting acoustic energy issued by the gear assembly. Also, the step of detecting acoustic energy issued by the gear assembly is provided with the step of placing a microphone n the vicinity of the gear assembly.
In accordance with a further embodiment of this method aspect of the invention, the drive and coast modes of operation are cyclical over a period that is shorter than a cycle period of the input of the gear assembly. Conversely, the period can be longer than a cycle period of the input of the gear assembly. This will depend, to an extent, upon the operating ratios within the system under test. In situations where the system under test is an electrical system, harmonics and signal distortions may affect the apparent cycle period in relation to the cycle period of the input energy.
In an advantageous embodiment, the first and second sensors are disposed at respective locations that are distal from each other, with the gear assembly interposed therebetween. This enables distinguishing between operating modalities of the system under test, as well as facilitating analysis of operating characteristics of the system under test that have directional components.